To start coding games you first must know the programming language itself. THE language used now for game programming is C++, but other languages like Java and Python can be used as well.
A website which you could use might be SoloLearn. They have courses which teach you various languages.
If you are not satisfied with their tutorials, I can teach you.
SmileBASIC I have no knowledge, unfortunately. But what I could do is grab a game, see the source code, and find out how to translate that code to another programming language.